Hybrid copper structure for advance interconnect usage

ABSTRACT

The present disclosure relates to a method of forming a BEOL metallization layer that uses different conductive materials (e.g., metals) to fill different size openings in an inter-level dielectric layer, and an associated apparatus. In some embodiments, the present disclosure relates to an integrated chip having a first plurality of metal interconnect structures disposed within a first BEOL metallization layer, which include a first conductive material. The integrated chip also has a second plurality of metal interconnect structures disposed within the first BEOL metallization layer at positions laterally separated from the first plurality of metal interconnect structures. The second plurality of metal interconnect structures have a second conductive material that is different than the first conductive material. By forming different metal interconnect structures on a same BEOL metallization layer using different conductive materials, gap-fill problems in narrow BEOL metal interconnect structures can be mitigated, thereby improving reliability of integrated chips.

BACKGROUND

Modern day integrated chips (ICs) often comprise billions of transistor devices disposed within a semiconductor substrate. Back-end-of-the-line (BEOL) metallization layers are used to connect the transistor devices to each other and to the outside world. BEOL metallization layers are stacked layers of small conductive metal wires and vias that are disposed within a dielectric material overlying the semiconductor substrate. The metal wires provide for lateral connections while the vias provide for vertical connections between metal wires. Typically, the stacked BEOL metallization layers increase in size as the metallization layers get further from the semiconductor substrate, such that tightly packed small metal wires are located near the transistor devices and larger metal wires are located near a top of the stack.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 illustrates a cross-sectional view of some embodiments of an integrated chip having a back-end-of-the-line (BEOL) metallization layer comprising laterally separated metal interconnect structures having different conductive materials.

FIG. 2 illustrates a cross-sectional view of some embodiments of an integrated chip having a BEOL metallization layer comprising laterally separated metal interconnect structures having different conductive materials.

FIG. 3 illustrates a flow diagram of some embodiments of a method of forming a BEOL metallization layer comprising laterally separated metal interconnect structures having different conductive materials.

FIGS. 4A-10 illustrate some embodiments of cross-sectional views showing a method of forming a BEOL metallization layer comprising laterally separated metal interconnect structures having different conductive materials.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

Over the past 15-20 years, copper has become a commonly used material for (back-end-of-the-line) BEOL metallization layers. Copper has a very high electrical conductivity, which provides for relatively low resistance on the BEOL and therefore good integrated chip performance. Copper metallization layers (e.g., metal wires and vias) are often formed using a damascene process in which copper is deposited into a patterned dielectric material. For example, in a dual damascene process a dielectric material is deposited over a semiconductor substrate. The dielectric material is selectively etched to form openings for a via (i.e., a via hole) and a metal wire (i.e., a metal trench). The openings are then filled with copper and a planarization process is performed to remove excess copper from the substrate.

As the size of integrated chip components has been scaled downward, the size of thin metallization layers (i.e., metallization layers used for local routing between transistors) have decreased. It has been appreciated that in emerging technology nodes (e.g., technology nodes having via holes and/or metal trenches with minimum dimensions less than 40 nm), gap-fill issues begin to arise which make it increasingly difficult for damascene processes to fill via holes and/or metal trenches with copper. For example, it is difficult to use copper damascene plating processes to fill openings having a minimum dimension of less than 30 nm, therefore resulting in the formation of voids (e.g., cavities devoid of copper) in resulting metal wires and vias. The voids can lead to electrical opens in a BEOL metallization layer that are detrimental to reliability of an integrated chip.

Accordingly, the present disclosure relates to a method of forming a BEOL metallization layer that mitigates gap-fill problems by using different conductive materials (e.g., metals) to fill different size openings in an inter-level dielectric (ILD) layer, and an associated apparatus. In some embodiments, the present disclosure relates to an integrated chip comprising a first plurality of metal interconnect structures disposed within a first BEOL metallization layer, which include a first conductive material. The integrated chip further comprises a second plurality of metal interconnect structures disposed within the first BEOL metallization layer at positions laterally separated from the first plurality of metal interconnect structures. The second plurality of metal interconnect structures comprise a second conductive material that is different than the first conductive material. By forming different metal interconnect structures on a same BEOL metallization layer using different conductive materials, gap-fill problems in narrow BEOL metal interconnect structures can be mitigated, thereby improving the reliability of an integrated chip.

FIG. 1 illustrates a cross-sectional view of some embodiments of an integrated chip 100 having a back-end-of-the-line (BEOL) metallization layer comprising laterally separated metal interconnect structures with different conductive materials.

The integrated chip 100 comprises a plurality of back-end-of-the-line (BEOL) metallization layers, 104 and 106, disposed within an inter-level dielectric (ILD) layer 108 overlying a semiconductor substrate 102. In various embodiments, the semiconductor substrate 102 may comprise any type of semiconductor body (e.g., silicon, silicon germanium (SiGe), SOI, etc.) such as a semiconductor wafer or one or more die on a wafer, as well as any other type of semiconductor and/or epitaxial layers formed thereon and/or otherwise associated therewith. In some embodiments, the ILD layer 108 may comprise one or more dielectric materials, such as a low-k dielectric material or an ultra-low-k (ULK) dielectric material, for example. In some embodiments, an etch stop layer (ESL) 116 may be disposed between the ILD layer 108 and the semiconductor substrate 102. In various embodiments, the ESL 116 may comprise nitride, silicon carbide, carbon-doped oxide, or other similar materials.

The plurality of BEOL metallization layers comprise a metal via layer 104 and an overlying metal wire layer 106. The metal via layer 104 comprises a plurality of vias 110 disposed within the ILD layer 108, which are configured to provide for vertical interconnections (i.e., interconnections in a direction perpendicular to a top surface of the semiconductor substrate 102). The metal wire layer 106 is configured to provide for lateral interconnections (i.e., interconnections in a direction parallel to a top surface of the semiconductor substrate 102).

The metal wire layer 106 comprises a first plurality of metal interconnect structures 112 and a second plurality of metal interconnect structures 114. The first plurality of metal interconnect structures 112 are laterally separated from the second plurality of metal interconnect structures 112 by the ILD layer 108. The first plurality of metal interconnect structures 112 have a smaller width (i.e., minimum dimension) than the second plurality of metal interconnect structures 114. For example, the first plurality of metal interconnect structures 112 have a first width w₁ and the second plurality of metal interconnect structures 114 have a second width w₂ that is greater than the first width w₁. In some embodiments, the first width w₁ has a value that is in range of between approximately 3 nm and approximately 30 nm, while the second width w₂ has a value that is greater than approximately 30 nm.

The first plurality of metal interconnect structures 112 include a first conductive material and the second plurality of metal interconnect structures 114 include a second conductive material that is different than the first conductive material. The first conductive material comprises a material having an ability to fill small gaps (i.e., small openings in the ILD layer 108) that are not able to be easily filled by the second conductive material. By using the first conductive material for metal interconnect structures having a relatively small width and the second conductive material for the metal interconnect structures having a larger width, gap-fill problems on BEOL metallization layers can be mitigated without substantially compromising performance (e.g., resistivity) of the metal wire layer 106. For example, in some embodiments, the first conductive material may comprise cobalt or tungsten, while the second conductive material may comprise copper. When deposited by a vapor deposition technique (e.g., chemical vapor deposition, atomic layer deposition, etc.), cobalt and tungsten offer better gap-fill capabilities than copper for openings having a small width/minimum dimension (e.g., less than or equal to approximately 30 nm). In some embodiments, the plurality of vias 110 may also comprise the first conductive material, so as to prevent gap-fill problems within the metal via layer 104.

In some embodiments, one or more of the plurality of vias 110 may vertically extend to a position that overlaps the second plurality of metal interconnect structures 114, such that the one or more of the plurality of vias 110 that are laterally aligned with of the second plurality of metal interconnect structures 114 extend to positions within the second plurality of metal interconnect structures 114. In other words, the one or more of the plurality of vias 110 that are laterally aligned with the second plurality of metal interconnect structures 114 abut the second plurality of metal interconnect structures 114 on three sides.

Although integrated chip 100 describes and illustrates a BEOL metal wire layer 106 comprising laterally separated metal interconnect structures having different conductive materials, it will be appreciated that the present disclosure is not limited to metal wire layers having different conductive materials. In other embodiments, laterally separated metal vias may also and/or alternatively have different conductive materials.

FIG. 2 illustrates a cross-sectional view of some embodiments of an integrated chip 200 having a BEOL metallization layer comprising laterally separated metal interconnect structures having different conductive materials.

The integrated chip 200 comprises a plurality of stacked BEOL metallization layers 104 a-204, which are disposed within a plurality of inter-level dielectric (ILD) layers 108 a-108 c overlying a semiconductor substrate 102. In some embodiments, etch stop layers (ESL) 116 a-116 c are disposed between the plurality of ILD layers 108 a-108 c. For example, a first ESL 116 a is disposed between a first ILD layer 108 a and a second ILD layer 108 b, a second ESL 116 b is disposed between the second ILD layer 108 b and a third ILD layer 108 c.

A first via layer 104 a and an overlying first metal wire layer 106 a are disposed within the first ILD layer 108 a. The first via layer 104 a comprises a plurality of vias 110 a. The first metal wire layer 106 a comprises a first plurality of metal interconnect structures 112 a having a first conductive material and a second plurality of metal interconnect structures 114 a having a second conductive material that is different than the first conductive material. In some embodiments, a first liner layer 206 a separates the first plurality of metal interconnect structures 112 a from the first ILD layer 108 a and a second liner layer 208 a separates the second plurality of metal interconnect structures 114 a from the first ILD layer 108 a. In some embodiments, the first liner layer 206 a and the second liner layer 208 a may comprise different materials. For example, in some embodiments, the first liner layer 206 a may comprise titanium (Ti), titanium nitride (TiN), tantalum (Ta), or tantalum nitride (TaN), while the second liner layer 208 a may comprise tantalum nitride (TaN), tantalum (Ta), cobalt (Co), ruthenium (Ru), or titanium nitride (TiN).

In some embodiments, the plurality of stacked BEOL metallization layers 104 a-204 may have different minimum width (i.e., minimum dimension) values. For example, metal wire layers 106 a and 106 b may have features having a first minimum width value (e.g., less than or equal to approximately 30-40 nm), while the metal wire layer 204 may have features having a second minimum width value that is greater than the first minimum width value (e.g., greater than or equal to approximately 40-50 nm). In some embodiments, the minimum width of metal wire layer 204 may be large enough so that gap-fill issues are not present in the metal wire layer 204. In such embodiments, metal wire layers 106 a and 106 b may comprise laterally separated metal wires including the first and second conductive materials, while metal wire layer 204 may comprise laterally separated metal wires including the first conductive material and not the second conductive material.

FIG. 3 illustrates a flow diagram of some embodiments of a method 300 of forming a BEOL metallization layer comprising laterally separated metal interconnect structures having different conductive materials.

While disclosed method 300 is illustrated and described herein as a series of acts or events, it will be appreciated that the illustrated ordering of such acts or events are not to be interpreted in a limiting sense. For example, some acts may occur in different orders and/or concurrently with other acts or events apart from those illustrated and/or described herein. In addition, not all illustrated acts may be required to implement one or more aspects or embodiments of the description herein. Further, one or more of the acts depicted herein may be carried out in one or more separate acts and/or phases.

At 302, a first plurality of metal interconnect structures comprising a first conductive material are formed within a back-end-of-the-line (BEOL) metallization overlying a semiconductor substrate. In some embodiments, the first plurality of metal interconnect structures may be formed by selectively masking an inter-level dielectric (ILD) layer according to a first masking layer that defines a plurality of narrow metal openings, at 304. At 306, the ILD layer is selectively etched to form the narrow metal openings within the ILD layer. At 308, the narrow metal openings are filled with a first conductive material to form the first plurality of metal interconnect structures.

At 310, a second plurality of metal interconnect structures, comprising a second conductive material that is different than the first conductive material, are formed within the BEOL metallization layer. In some embodiments, the second plurality of metal interconnect structures may be formed by selectively masking the ILD layer to define wide metal openings, at 312. At 314, the ILD layer is then selectively etched to form the wide metal openings within the ILD layer. At 316, the wide metal openings are filled with a second conductive material to form the second plurality of metal interconnect structures.

At 318, a planarization process may be performed to remove excess of the first and second conductive materials from the substrate, in some embodiments.

It will be appreciated that method 300 may be performed according to different back-end-of-the-line fabrication techniques. For example, in some embodiments, the method 300 may be performed according to a damascene process. In such embodiments, the first and second plurality of metal interconnect structures may be implemented as a metal layer of a dual damascene process or as a metal layer of a single damascene process. In other embodiments, the method 300 may be performed according to a non-damascene process.

FIGS. 4A-10 illustrate some embodiments of cross-sectional views showing a method 300 of forming a BEOL metallization layer comprising laterally separated metal interconnect structures having different conductive materials. Although FIGS. 4A-10 are described in relation to method 300, it will be appreciated that the structures disclosed in FIGS. 4A-10 are not limited to such a method, but instead may stand alone as structures independent of the method 300.

FIGS. 4A-4B illustrates some embodiments of cross-sectional views, 400 and 412, corresponding to acts 304-306.

FIG. 4A illustrates some embodiments of a cross-sectional view of an implementation of acts 304-306 as a dual damascene process. As shown in cross-sectional view 400, an inter-level dielectric (ILD) layer 402 is formed over a semiconductor substrate 102. In some embodiments, the ILD layer 402 may comprise a low-k dielectric layer or an ultra-low-k (ULK) dielectric layer, formed by way of a thermal process or a deposition process. In some embodiments, an etch stop layer (ESL) 116 may be formed between the ILD layer 402 and the semiconductor substrate 102. In various embodiments, the ESL 116 may comprise nitride, silicon carbide, carbon-doped oxide, or other similar materials.

The ILD layer 402 is exposed to a first etchant 404 that is configured to selectively etch the first ILD layer 402 according to a first masking layer 406 to form a plurality of narrow metal openings, 408 and 410. In some embodiments, the first masking layer 406 may comprise a photoresist layer. The plurality of narrow metal openings, 408 and 410, have a first width w₁. In some embodiments, the first width w₁ may have a value that is less than or equal to approximately 30 nm. In some embodiments, the first etchant 404 may comprise a plasma etchant having an etching chemistry comprising one or more of fluorine (F), Tetrafluoromethane (CF₄), ozone (O₂), or C₄F₈ (Octafluorocyclobutane), for example. In some embodiments, the plurality of narrow metal openings, 408 and 410, may comprise a narrow metal trench opening 408 extending through a metal wire layer 106 and/or a narrow metal trench and via opening 410 extending through a metal via layer 104 and the metal wire layer 106.

FIG. 4B illustrates some embodiments of a cross-sectional view of an implementation of acts 304-306 as a single damascene process. As shown in cross-sectional view 400, the narrow metal openings, 408 and 410, may comprise a metal trench opening disposed over a via 110.

FIG. 5 illustrates some embodiments of a cross-sectional view 500 corresponding to act 308.

As shown in cross-sectional view 500, a first conductive material 502 is deposited to fill the plurality of narrow metal openings, 408 and 410. In some embodiments, the first conductive material 502 may extend out of the narrow metal openings, 408 and 410, to form a continuous layer that extends over a top surface of the ILD layer 402. The first conductive material 502 comprises a material having an ability to fill narrow metal openings, 408 and 410, without forming voids. In some embodiments, the first conductive material 502 may comprise tungsten (W) or cobalt (Co) deposited using a deposition technique such as a chemical vapor deposition (CVD) process or an atomic layer deposition (ALD) process.

For example, in some embodiments, the first conductive material 502 may comprise cobalt deposited using a CVD process performed within a processing chamber held at a temperature in a range of between approximately 100° C. and approximately 300° C. and at a pressure in a range of between approximately 10 torr and approximately 50 torr. In such embodiments, the CVD process may use processing gases of C₅H₅(CO)₂Co and H₂. In other embodiments, the first conductive material 502 may comprise cobalt deposited using an ALD process performed within a processing chamber held at a temperature in a range of between approximately 100° C. and approximately 300° C. and at a pressure in a range of between approximately 0.1 torr and approximately 10 torr. In such embodiments, the ALD process may use processing gases of ((C₅H₅)CO(CO)₂), H₂, N₂, and NH₃.

In some other embodiments, the first conductive material 502 may comprise tungsten deposited using a CVD process performed within a processing chamber held at a temperature in a range of between approximately 300° C. and approximately 500° C. and at a pressure in a range of between approximately 1 torr and approximately 10 torr. In such embodiments, the CVD process may use processing gases of WF₆ and H₂. In other embodiments, the first conductive material 502 may comprise tungsten deposited using an ALD process performed within a processing chamber held at a temperature in a range of between approximately 200° C. and approximately 400° C. and at a pressure in a range of between approximately 1 torr and approximately 10 torr. In such embodiments, the ALD process may use processing gases WF₆ and B₂H₆.

FIG. 6 illustrates some embodiments of a cross-sectional view 600 corresponding to act 312.

As shown in cross-sectional view 600, a second masking layer 602 is selectively formed over the first conductive material 502. The second masking layer 602 defines a plurality of wide metal openings 604 within the ILD layer 402. In some embodiments, the second masking layer 602 may comprise a photoresist layer. In some embodiments, the photoresist layer may be used to selectively etch the first conductive material 502 so that the first conductive material 502 can be used as a hard mask overlying the ILD layer 402.

FIG. 7 illustrates some embodiments of a cross-sectional view 700 corresponding to act 314.

As shown in cross-sectional view 700, the ILD layer 402 is exposed to a second etchant 702 that is configured to selectively etch the ILD layer 402 to form a plurality of wide metal openings 704. In some embodiments, the second etchant 702 may comprise a plasma etchant having an etching chemistry comprising one or more of F, CF₄, O₂, or C₄F₈, for example. In some embodiments, the plurality of wide metal openings 704 may have a second width w₂ that is larger than the first width W. In some embodiments, the second width w₂ has a value that is greater than or equal to approximately 30 nm.

In some embodiments, the second etchant 702 is configured to over etch the ILD layer 402 to a position that causes plurality of wide metal openings 704 to extend within the ILD layer 402 to a vertical location that is below a top surface of one or more of the plurality of vias 110. In such embodiments, one or more of the plurality vias 110 extend outward from the bottom of the plurality of wide metal openings 704 as positive reliefs. By causing the plurality of vias 110 to extend outward from the bottom of the plurality of wide metal openings 704, a good electrical connection is made between the plurality of vias 110 and an overlying metal layer disposed within the plurality of wide metal openings 704.

FIG. 8 illustrates some embodiments of a cross-sectional view 800 corresponding to act 316.

As shown in cross-sectional view 800, a second conductive material 802 is deposited to fill the plurality of wide metal openings 704. The second conductive material 802 is different than the first conductive material 502, so that different conductive materials (502 and 802) are laterally disposed apart from one another. In some embodiments, the second conductive material 802 may comprise copper. In some embodiments, the second conductive material 802 may be deposited by way of a plating process (e.g., an electro plating process, an electro-less plating process). In other embodiments, the second conductive material 802 may be deposited using a vapor deposition technique (e.g., CVD, PVD, ALD, etc.).

FIG. 9 illustrates some embodiments of a cross-sectional view 900 corresponding to act 318.

As shown in cross-sectional view 900, a planarization process is performed to form a flat surface along line 902 by removing excess of the first and second conductive materials, 502 and 802, from the substrate. In some embodiments, the planarization process may comprise a chemical mechanical polishing (CMP) process.

It will be appreciated that method 300 may be iteratively performed to form a plurality of stacked BEOL metallization layers overlying the semiconductor substrate 102. FIG. 10 illustrates some embodiments of a cross-sectional view 1000 of an integrated chip having a BEOL stack comprising a plurality of BEOL metallization layers formed according to method 300. As shown in cross-sectional view 1000, the integrated chip has a first metal wire layer 106 a comprising laterally separated metal interconnect structures having different conductive materials and a second metal wire layer 106 b comprising laterally separated metal interconnect structures having different conductive materials.

Therefore, the present disclosure relates to a method of forming a BEOL metallization layer that mitigates gap-fill problems by using different conductive materials (e.g., metals) to fill different size openings in an inter-level dielectric (ILD) layer, and an associated apparatus.

In some embodiments, the present disclosure relates to an integrated chip. The integrated chip comprises a first plurality of metal interconnect structures disposed within a first back-end-of-the-line (BEOL) metallization layer and comprising a first conductive material. The integrated chip further comprises a second plurality of metal interconnect structures disposed within the first BEOL metallization layer at positions laterally separated from the first plurality of metal interconnect structures, wherein the second plurality of metal interconnect structures comprise a second conductive material that is different than the first conductive material.

In other embodiments, the present disclosure relates to an integrated chip. The integrated chip a first plurality of metal interconnect structures disposed within a first metal wire layer and comprising a first metal. The integrated chip further comprises a second plurality of metal interconnect structures disposed within the first metal wire layer at positions laterally separated from the first plurality of metal interconnect structures by an inter-level dielectric (ILD) layer, wherein the second plurality of metal interconnect structures comprise a second metal that is different than the first metal. The first plurality of metal interconnect structures have a first width and the second plurality of metal interconnect structures have a second width that is larger than the first width.

In yet other embodiments, the present disclosure relates to a method of forming a back-end-of-the-line (BEOL) metallization layer. The method comprises forming a first plurality of metal interconnect structures comprising a first conductive material within a first BEOL metallization layer overlying a semiconductor substrate. The method further comprises forming a second plurality of metal interconnect structures comprising a second conductive material within the first BEOL metallization at positions laterally separated from the first plurality of metal interconnect structures, wherein the second conductive material is different than the first conductive material.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 

What is claimed is:
 1. An integrated chip, comprising: a first plurality of metal interconnect structures disposed within a first back-end-of-the-line (BEOL) metallization layer and comprising a first conductive material; and a second plurality of metal interconnect structures disposed within the first BEOL metallization layer at positions laterally separated from the first plurality of metal interconnect structures, wherein the second plurality of metal interconnect structures comprise a second conductive material that surrounds the first conductive material and wherein the first conductive material protrudes outward from a bottom surface of the second conductive material.
 2. The integrated chip of claim 1, wherein the first plurality of metal interconnect structures have a first width and the second plurality of metal interconnect structures have a second width that is larger than the first width.
 3. The integrated chip of claim 2, wherein the first width is in a range of between approximately 3 nm and approximately 30 nm.
 4. The integrated chip of claim 1, wherein the first conductive material comprises cobalt or tungsten, and wherein the second conductive material comprises copper.
 5. The integrated chip of claim 1, wherein the first BEOL metallization layer comprises a metal wire layer comprising a plurality of metal wires configured to provide for lateral interconnections.
 6. The integrated chip of claim 1, further comprising: a via layer comprising a plurality of vias abutting a lower surface of the second plurality of metal interconnect structures, wherein the first conductive material continuously extends from the plurality of vias to a location nested within the second conductive material within the second plurality of metal interconnect structures.
 7. The integrated chip of claim 6, wherein the plurality of vias have sidewalls and a top surface that abut the second conductive material.
 8. The integrated chip of claim 6, wherein the second conductive material has a first lower surface overlying the plurality of vias and a second lower surface that is laterally offset from the plurality of vias, wherein the first lower surface is vertically offset from the second lower surface.
 9. The integrated chip of claim 1, wherein the first plurality of metal interconnect structures are separated from the second plurality of metal interconnect structures by an inter-level dielectric (ILD) layer.
 10. The integrated chip of claim 9, further comprising: a first liner layer disposed between the first plurality of metal interconnect structures and the ILD layer; and a second liner layer disposed between the second plurality of metal interconnect structures and the ILD layer, wherein the first liner layer and the second liner layer comprise different materials.
 11. The integrated chip of claim 1, further comprising: an overlying metal wire layer comprising a plurality of metal wires comprising the second conductive material.
 12. An integrated chip, comprising: a first plurality of metal interconnect structures disposed within a first metal wire layer and comprising a first metal; a second plurality of metal interconnect structures disposed within the first metal wire layer at positions laterally separated from the first plurality of metal interconnect structures by an inter-level dielectric (ILD) layer, wherein the second plurality of metal interconnect structures comprise the first metal and a second metal that is different than the first metal; and wherein the second metal laterally separates the first metal from sidewalls of the second plurality of metal interconnect structures.
 13. The integrated chip of claim 12, wherein the first metal comprises cobalt or tungsten, and wherein the second metal comprises copper.
 14. The integrated chip of claim 12, further comprising: an overlying metal wire layer comprising a plurality of metal wires comprising the second metal.
 15. The integrated chip of claim 12, wherein the first plurality of metal interconnect structures have a first width and the second plurality of metal interconnect structures have a second width that is larger than the first width, and wherein the first width is in a range of between approximately 3 nm and approximately 30 nm.
 16. The integrated chip of claim 12, further comprising: a via layer comprising a plurality of vias abutting a lower surface of the second plurality of metal interconnect structures, wherein the first metal continuously extends from the plurality of vias to a location nested within the second metal within the second plurality of metal interconnect structures.
 17. The integrated chip of claim 16, wherein one or more of the plurality of vias are laterally aligned with one or more of the second plurality of metal interconnect structures and extend to positions that vertically overlap the one or more of the second plurality of metal interconnect structures.
 18. An integrated chip, comprising: a dielectric structure arranged over a substrate; a first metal interconnect structure arranged within the dielectric structure and comprising a first metal, wherein the first metal has sidewalls that define a recess within a lower surface of the first metal facing the substrate; a second metal interconnect structure arranged within the dielectric structure and comprising a second metal that is different than the first metal, wherein the first metal interconnect structure is laterally separated from the second metal interconnect structure by the dielectric structure; and a lower metal interconnect structure comprising the second metal and extending from within the recess to a location between the first metal interconnect structure and the substrate.
 19. The integrated chip of claim 18, wherein the lower metal interconnect structure has a width that is substantially equal to a width of the second metal interconnect structure.
 20. The integrated chip of claim 18, further comprising: a first liner layer disposed between the first metal interconnect structure and the dielectric structure, wherein the lower metal interconnect structure extends through a section of the first liner arranged along a lower surface of the first metal interconnect structure. 